A self-powered SECE (synchronized electric charge extraction)-based energy sensor is developed and applied to measuring shaft torque. The design is based on the setup of two-point magnetic plucking allowing the torque-induced phase angles between two pairs of magnets. The result shows the realization of broadband energy harvesting due to inducing mixed resonant modes of vibration from frequency up-conversion and enhancement by SECE. In addition, torque sensing is achieved by measuring the variation of modal amplitude of voltage response against the phase shift angles. For the case of torque sensing operated at the second resonant mode, the phase angle against the voltage is multi-valued. A solution for the unique sensing is to develop a CNN (convolution neural network) classifier capable of distinguishing various voltage waveforms from different phase angles. The prediction agrees reasonably with experiment.
The article presents a novel MISO (multi-input-single-output) diagnostic system suitable for spatial condition monitoring of bearing/gearbox instruments with multi-location defects. The sensor array consists of three piezoelectric patches: one is attached to the surface of the bearing house and the other two connected in parallel are mounted on the wall of the planetary gear. These two sets of patches are electrically connected in series for sensing the fault signals whose sources of anomalies come from either the bearing or the gear. They offer an advantage of allowing a single voltage output from multiple inputs. In addition, two inductances are connected to the sensor array to form LC resonant circuits for filtering the irrelevant noise at high frequency. A convolutional neural network (CNN) classifier is trained by 12x150 FFT spectrums. The result from the testing data with 12x10 FFT spectrums shows that the average accuracy is achieved to be as high as 92:5%, confirming the soundness of the proposed model.
The article presents a novel idea for the fault diagnostics of the timing belt based on developing a piezoelectric energy sensor attached to the synchronized electric charge extraction (SECE) interface. The device is composed of a piezoelectric cantilever beam with a tip magnet impulsively excited by another small magnet attached on the surface of a moving timing belt. As a result, energy is harvested by frequency up-conversion mechanism operated under magnetic plucking. It is observed that the extent to which power harvested from the failing belt is higher than that from the healthy belt, giving rise to the basis for condition monitoring of the timing belt by detecting the output power. In addition, the analysis shows that the power sensitivity to the magnetic distance can be enhanced to 145% by the SECE interface circuit in comparison with the standard (STD) interface circuit. The consequence of it is that the SECE case exhibits a more accurate decision boundary determined by the logistic regression to classify the healthy and flawed states, as confirmed by the experiment.
The article presents the development of a self-powered rectified electromagnetic energy harvester (EMEH) under low frequency excitations. To overcome the drawback of low output voltage across the small optimal load, it is proposed to use the transistor-based rectifier biased by the self-powered SECE-based piezoelectric energy harvester (PEH). In addition, the buck-boost converter controlled by the self-powered SSHI-based PEH is im- plemented for the maximum power point tracking. A semi-analytic model is developed for predicting the peak power and the optimal load used for designing the buck-boost converter. The prediction is then validated by experiment showing 1.5 mW optimal output power. Further, it is found that the 0.22 low rectified voltage is increased up to 2.5 V by the proposed SSHI-based voltage boosting technique. It offers advantages of zero quiescent power dissipation and the ease of tuning the input impedance of the buck-boost converter by varying the SSHI load impedance.
The article presents the study of a novel self-powered SECE (synchronized electric charge extraction) circuit for scavenging piezoelectric energy under low-frequency shock excitation. Specifically, the device consists of a piezoelectric cantilever beam whose tip magnet is impulsively excited by a rotating magnet. It is attached to a load-independent SECE circuit with the advantage of power enhancement at low-level output voltage. The proposed circuit includes an envelope detector for voltage detection, a voltage divider for minimizing the switching delay and a diode for recovering the charge on the detection capacitance. The result shows that the predicted harvested power agrees well with the experimental observations. In addition, the power ripples are significantly reduced due to the larger electric-induced damping drawn from the SECE technique. Finally, the load-independent property makes the observed SECE power remain constant within the output voltage operated at around 2-5 volt, and therefore outperforms the standard DC power.
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